Semiconductor device and method for manufacturing the same

ABSTRACT

In a semiconductor device having a first MIS transistor on a semiconductor substrate, the first MIS transistor includes a p-type semiconductor layer, a first gate insulating film, a first gate electrode, a first sidewall insulating film including at least a first sidewall, an n-type extension diffusion layer, and an n-type impurity diffusion layer. The first sidewall is not formed at the side faces of the first gate electrode on the p-type semiconductor layer. An insulating film having tensile stress is formed on the semiconductor substrate so as to cover the first MIS transistor.

CROSS REFERENCE TO RELATED APPLICATIONS

This Non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2005-310244 filed in Japan on Oct. 25,2005, the entire contents of which are hereby incorporated by reference.

BACKGROUND ART

The present invention relates to a semiconductor device and a method formanufacturing it, and specifically relates to a semiconductor devicethat exerts high drivability by appropriately adjusting the conductivityof a carrier in a channel region of an MIS (Metal InsulatorSemiconductor) transistor.

In various methods for increasing drivability of an MIS transistor,there is a method of increasing a drain current as a drive current. Ofseveral measures of determining the drain current, carrier mobility islisted.

In general, it is known that the carrier mobility can be changed in sucha manner that scattering rate or an effective mass of the carrier ischanged by changing the lattice constant of atoms composing asemiconductor substrate.

Under the circumstances, a technique has been proposed in which themobility of the carrier passing through the lattices is changed in sucha manner that a film having tensile stress is disposed on an MIStransistor to increase the lattice constant of silicon atoms in achannel region of the transistor.

A conventional semiconductor device which focuses attention on thecarrier mobility in the channel region will be described below withreference to FIG. 12. FIG. 12 is a section of a structure of a main partof the conventional semiconductor device.

As shown in FIG. 12, an NMOS (N-type channel Metal Oxide Semiconductor)region 503 defined by an element isolation 502 and including a p-typewell is formed in a semiconductor substrate 501 made of, for example,silicon. A gate insulating film 511 and a gate electrode 512 are formedin the upward order on the NMOS region 503. Further, n-type source/draindiffusion regions 517 serving as impurity diffusion layers to which ann-type impurity ion such as arsenic is implanted are formed in the NMOSregion 503. Each n-type source/drain diffusion layer 517 includes ann-type extension diffusion layer 516 which is formed in a region beloweach side face of the gate electrode 512 and of which junction depth iscomparatively shallow. Sidewalls 513 made of SiN are formed at the sidefaces of the gate insulating film 51 and the gate electrode 512. Asilicide layer 514 is formed on the gate electrode 511 and the n-typesource/drain diffusion layers 517. Over the entirety of thesemiconductor substrate 501, a liner film 530 made of a silicon nitridefilm having tensile stress and formed by LP-CVD is formed so as to coverthe element isolation 502, the gate electrode 512, the sidewall 513, andthe silicide layer 514 (see, for example, Japanese Patent ApplicationLaid Open Publication No. 2002-198368A). Herein, the silicon nitridefilm having tensile stress means a silicon nitride film which exertstensile stress on a channel region in the direction of the gate length.

In the conventional semiconductor device shown in FIG. 12, the tensilestress that the liner film 530 has increases the lattice constant of thesilicon atoms composing the channel region of the semiconductorsubstrate 501.

However, the sidewall 513 formed on each side face of the gateinsulating film 511 and the gate electrode 512 inhibits the tensilestress that the liner film 530 has from being transmitted effectively tothe channel region of the semiconductor substrate 501, attaining aninsufficient increase in lattice constant of the silicon atoms in thechannel region of the semiconductor substrate 501. As a result, thecarrier mobility increases insufficiently.

SUMMARY OF THE INVENTION

Each mobility of holes and electrons as carriers increases or decreasesaccording to a direction of the tensile stress applied to the channelregion. For example, when the channel direction is set along a crystalorientation of <110> and the tensile stress is applied in the channeldirection, the electron mobility increases while the hole mobilitydecreases. In contrast, when the channel direction is set along acrystal orientation of <100> and the tensile stress is applied in thechannel direction, the electron mobility increases while the holemobility decreases less. For this reason, the direction of the tensilestress to be applied must be set appropriately. Particularly, thedirection of the tensile stress to be applied is a key in the case whereboth an NMOS region and a PMOS region are provided on the samesemiconductor substrate.

In view of the foregoing, the present invention has its object ofincreasing carrier mobility in a channel region of an NMIS region.

For attaining the above object, a first aspect of the present inventionprovides a semiconductor device, including a semiconductor substrate, anelement isolation, a first MIS transistor on the semiconductorsubstrate, and an insulating film which has tensile stress and which isformed on the semiconductor substrate so as to cover the first MIStransistor, wherein the first MIS transistor includes: a p-typesemiconductor layer defined by the element isolation in thesemiconductor substrate; a first gate insulating film formed on thep-type semiconductor layer; a first gate electrode formed on the firstgate insulating film and the element isolation so as to lie astride thep-type semiconductor layer; a first sidewall insulating film formed ateach side face of the first gate electrode on the element isolation andincluding at least a first sidewall; an n-type extension diffusion layerformed outwards from the first gate electrode in the p-typesemiconductor layer; and an n-type impurity diffusion layer formed in aregion of the p-type semiconductor layer which is adjacent to the n-typeextension diffusion layer, and the first sidewall is not formed at eachside face of the first gate electrode on the p-type semiconductor layer.

In the semiconductor device according to the first aspect of the presentinvention, the first sidewalls formed at the side faces of the gateelectrode are removed on the p-type semiconductor layer, so that thetensile stress that the insulating film has is applied efficiently tothe channel region of the p-type semiconductor layer. Thus, the tensilestress can be increased in the channel region of the p-typesemiconductor layer. As a result, the electron mobility in the channelregion of the p-type semiconductor layer increases and the transistorpower also increases.

The semiconductor device according to the first aspect of the presentinvention further includes a second MIS transistor, wherein the secondMIS transistor includes: an n-type semiconductor layer defined by theelement isolation in the semiconductor substrate; a second gateinsulating film formed on the n-type semiconductor layer; a second gateelectrode formed on the second gate insulating film; a second sidewallinsulating film formed at each side face of the second gate electrodeand including at least a second sidewall; a p-type extension diffusionlayer formed outwards from the second gate electrode in the n-typesemiconductor layer; and a p-type impurity diffusion layer formed in aregion of the n-type semiconductor layer which is adjacent to the p-typeextension diffusion layer, and the insulating film having tensile stressfurther covers the second MIS transistor.

With the above arrangement in which the n-type transistor and the p-typetransistor are formed on the same semiconductor substrate, the electronmobility can be increased in the channel region of the p-type transistorwhile the hole mobility can be decreased in the channel region of then-type transistor.

In the semiconductor device according to the first aspect of the presentinvention, the first sidewall insulating film may not be formed at eachside face of the first gate electrode on the p-type semiconductor layer.

In the semiconductor device according to the first aspect of the presentinvention, it is preferable that the first sidewall insulating filmfurther includes an L-shaped insulating film in an L shape in sectionwhich extends between the first sidewall and each side face of the firstgate electrode and between the first sidewall and the element isolationand the L-shaped insulating film extends to each side face of the firstgate electrode on the p-type semiconductor layer.

With the above arrangement, a region where the insulating film havingthe tensile stress and the semiconductor substrate are in direct contactwith each other is reduced, thereby suppressing formation of aninterface state which would involve an adverse influence on thecharacteristic of the transistor.

In this case, the L-shaped insulating film may include: a firstinsulating film in an I shape in section which is formed at each sideface of the first gate electrode; and a second insulating film in an Lshape in section which is formed at a side face of the first insulatingfilm.

A semiconductor device according to a second aspect of the presentinvention includes a semiconductor substrate, an element isolation, afirst MIS transistor and a second MIS transistor, the first MIStransistor and the second MIS transistor being formed in thesemiconductor substrate, and an insulating film having tensile stresswhich is formed on the semiconductor substrate so as to cover the firstMIS transistor and the second MIS transistor, wherein the first MIStransistor includes: a p-type semiconductor layer defined by the elementisolation in the semiconductor substrate; a first gate insulating filmformed on the p-type semiconductor layer; a first gate electrode formedon the first gate insulating film; an n-type extension diffusion layerformed outwards from the first gate electrode in the p-typesemiconductor layer; and an n-type impurity diffusion layer formed in aregion of the p-type semiconductor layer which is adjacent to the n-typeextension diffusion layer, the second MIS transistor includes: an n-typesemiconductor layer defined by the element isolation in thesemiconductor substrate; a gate insulating film formed on the n-typesemiconductor layer; a second gate electrode formed on the second gateinsulating film; a sidewall insulating film formed at each side face ofthe second gate electrode and including at least a sidewall; a p-typeextension diffusion layer formed outwards from the second gate electrodein the n-type semiconductor layer; and a p-type impurity diffusion layerformed in a region of the n-type semiconductor layer which is adjacentto the n-type extension diffusion layer, and no sidewall is formed ateach side face of the first gate electrode.

In the semiconductor device according to the second aspect of thepresent invention in which the n-type transistor and the p-typetransistor are formed on the same semiconductor substrate, no sidewallsare formed at the side faces of the gate electrode of the n-typetransistor. Accordingly, the tensile stress that the insulating film hasis applied efficiently to the channel region of the n-type transistor,increasing the tensile stress in the channel region. This increases theelectron mobility in the channel region of the n-type transistor toincrease the transistor power. On the other hand, the sidewalls are notformed at the side faces of the gate electrode of the p-type transistor,which has no need to increase the drivability, so that the tensilestress does not increase in the channel region of the p-type transistor.

In the semiconductor device according to the second aspect of thepresent invention, the first sidewall insulating films may not be formedat the side faces of the first gate electrode on the p-typesemiconductor layer.

In the semiconductor device according to the second aspect of thepresent invention, no sidewall insulating film may be formed at eachside face of the first gate electrode.

In the semiconductor device according to the second aspect of thepresent invention, it is preferable that the sidewall insulating filmfurther includes an L-shaped insulating film in an L shape in sectionwhich extends between the sidewall and each side face of the second gateelectrode and between the sidewall and the n-type semiconductor layerand another L-shaped insulating film is formed at each side face of thefirst gate electrode.

With the above arrangement, a region where the insulating film havingthe tensile stress and the semiconductor substrate are in direct contactwith each other is reduced, thereby suppressing formation of aninterface state which would involve an adverse influence on thecharacteristic of the transistors.

In this case, the L-shaped insulating films included in the sidewallinsulating film may include a first insulating film in an I shape insection which is formed at each side face of the first gate electrodeand a second insulating film in an L shape in section which is formed atthe side face of the first insulating film.

A first aspect of the present invention provides a semiconductor devicemanufacturing method which includes the steps of: (a) forming a p-typesemiconductor layer so as to be defined by an element isolation in asemiconductor substrate; (b) forming a gate insulating film on thep-type semiconductor layer and forming a gate electrode on the gateinsulating film and the element isolation so as to lie astride thep-type semiconductor layer; (c) forming an n-type extension diffusionlayer in a region of the p-type semiconductor layer which is locatedbelow each side of the gate electrode; (d) forming, after the step (c),a sidewall insulating film including at least a sidewall at each sideface of the gate electrode; (e) forming an n-type impurity diffusionlayer in a region of the p-type semiconductor layer which is locatedbelow a side of the sidewall insulating film so as to be adjacent to then-type extension diffusion layer; (f) selectively removing, after thestep (e), a part of the sidewall which is located on the p-typesemiconductor layer; and (g) forming, after the step (f), an insulatingfilm having tensile stress over the entirety of the semiconductorsubstrate, wherein the sidewall insulating film including the sidewallis formed between each side face of the gate electrode on the elementisolation and the insulating film.

In the semiconductor device manufacturing method according to the firstaspect of the present invention, the sidewall insulating films formed atthe side faces of the gate electrode on the p-type semiconductor layerare removed. Hence, the tensile stress that the insulating film has isefficiently applied to the channel region of the p-type semiconductorlayer, increasing the tensile stress in the channel region of the p-typesemiconductor layer. As a result, the electron mobility in the channelregion of the p-type semiconductor layer increases, and the transistorpower increases. Further, the element isolation can be covered with theresist pattern when the sidewalls on the p-type semiconductor layer isremoved, thereby preventing the element isolation from damage byetching. An interface state, which causes degradation of the transistorperformance, is formed in such a manner that the element isolation isdamaged by etching to allow the p-type semiconductor layer to expose tothe air. However, in this method, formation of the interface state isprevented with no damage by etching, suppressing the degradation of thetransistor performance.

In the semiconductor device manufacturing method according to the firstaspect of the present invention, it is preferable that the sidewallinsulating film further includes an L-shaped insulating film at eachside face of the gate electrode and the sidewall is formed on a sideface and the bottom face of the L-shaped insulating film.

This arrangement reduces a region where the insulating film having thetensile stress and the semiconductor substrate are in direct contactwith each other, suppressing formation of an interface state which wouldinvolve an adverse influence on the characteristic of the transistor.

In the semiconductor device manufacturing method according to the firstaspect of the present invention, in the step (f), a part of the sidewallinsulating film which is located on the p-type semiconductor layer isremoved.

A semiconductor device manufacturing method according to a second aspectof the present invention includes the steps of: (a) forming a p-typesemiconductor layer and an n-type semiconductor layer so as to bedefined by an element isolation in a semiconductor substrate; (b)forming a first gate electrode on the p-type semiconductor layer with afirst gate insulating film interposed; (c) forming a second gateelectrode on the n-type semiconductor layer with a second gateinsulating film interposed; (d) forming an n-type extension diffusionlayer in a region of the p-type semiconductor layer which is locatedbelow each side of the first gate electrode; (e) forming a p-typeextension diffusion layer in a region of the n-type semiconductor layerwhich is located below each side of the second gate electrode; (f)forming, after the step (d) and the step (e), a first sidewallinsulating film including at least a first sidewall at each side face ofthe first gate electrode and forming a second sidewall insulating filmincluding at least a second sidewall at each side face of the secondgate electrode; (g) forming an n-type impurity diffusion layer in aregion of the p-type semiconductor layer which is located below a sideof the first sidewall insulating film so as to be adjacent to the n-typeextension diffusion layer; (h) forming a p-type impurity diffusion layerin a region of the n-type semiconductor layer which is located below aside of the second sidewall insulating film so as to be adjacent to thep-type extension diffusion layer; (i) removing, after the step (g) andthe step (h), at least a part of the first sidewall which is located onthe p-type semiconductor layer; and (j) forming, after the step (i), aninsulating film having tensile stress over the entirety of thesemiconductor substrate, wherein the second sidewall insulating film isformed between each side face of the second gate electrode and theinsulating film.

In the semiconductor device manufacturing method according to the secondaspect of the present invention, where the n-type transistor and thep-type transistor are formed on the same semiconductor substrate, thesidewalls at the side faces of the gate electrode of the n-typetransistor are removed. Accordingly, the tensile stress that theinsulating film has is applied efficiently to the channel region of then-type transistor, increasing the tensile stress in the channel regionof the n-type transistor. This increases the electron mobility in thechannel region of the n-type transistor to increase the transistorpower. On the other hand, the sidewalls are not removed on the sidefaces of the gate electrode of the p-type transistor, which has no needto increase the drivability, so that the tensile stress in the channelregion of the p-type transistor does not increase.

In the semiconductor device manufacturing method according to the secondaspect of the present invention, it is preferable that the firstsidewall insulating film further includes an L-shaped insulating filmformed at each side face of the first gate electrode, and the firstsidewall is formed on a side face and the bottom face of the L-shapedinsulating film.

The above arrangement reduces a region where the insulating film havingthe tensile stress and the semiconductor substrate are in direct contactwith each other, suppressing formation of an interface state which wouldinvolve an adverse influence on the characteristic of the transistors.

In this case, at least a part of the first sidewall insulating filmwhich is formed on the p-type semiconductor layer is removed in the step(i).

As described above, in the semiconductor device and the manufacturingmethod thereof according to one aspect of the present invention, thetensile stress in the channel region of the p-type semiconductor layeris increased to increase the electron mobility in the channel region ofthe p-type semiconductor layer. As a result, the transistor powerincreases.

Further, in the case where the n-type transistor and the p-typetransistor are formed on the same semiconductor substrate, the electronmobility can be increased in the channel region of the n-type transistorwhile the hole mobility can be decreased in the channel region of thep-type transistor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a main part of a semiconductor deviceaccording to Embodiment 1 of the present invention.

FIG. 2A and FIG. 2B are sections showing the main part of thesemiconductor device according to Embodiment 1 of the present invention,wherein FIG. 2A is a section taken along the line IIa-IIa in FIG. 1 andFIG. 2B is a section taken along the line IIb-IIb in FIG. 1.

FIG. 3A to FIG. 3F are sections of the main part, each showing asemiconductor device manufacturing method according to Embodiment 1 ofthe present invention.

FIG. 4A to FIG. 4F are sections of the main part, each showing asemiconductor device manufacturing method according to Embodiment 1 ofthe present invention.

FIG. 5A to FIG. 5F are sections of the main part, each showing asemiconductor device manufacturing method according to Embodiment 1 ofthe present invention.

FIG. 6 is a section showing a main part of a semiconductor deviceaccording to Embodiment 2 of the present invention.

FIG. 7A to FIG. 7D are sections of the main part, each showing asemiconductor device manufacturing method according to Embodiment 2 ofthe present invention.

FIG. 8A to FIG. 8D are sections of the main part, each showing asemiconductor device manufacturing method according to Embodiment 2 ofthe present invention.

FIG. 9A and FIG. 9B are sections of the main part, each showing asemiconductor device manufacturing method according to Embodiment 2 ofthe present invention.

FIG. 10 is a section showing a main part of a semiconductor deviceaccording to Embodiment 3 of the present invention.

FIG. 11A to FIG. 11C are sections of the main part, each showing asemiconductor device manufacturing method according to Embodiment 3 ofthe present invention.

FIG. 12 is a section showing a main part of a conventional semiconductordevice.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Each embodiment of the present invention will be descried with referenceto the accompanying drawings.

Embodiment 1

A semiconductor device and a method for manufacturing it according toEmbodiment 1 of the present invention will be described below withreference to the drawings. Wherein, tensile stress in the followingdescription means stress to be applied in a direction of the gate lengthof a transistor in a channel region. Also, the channel direction is setalong a crystal orientation of <110> as an example.

The semiconductor device according to Embodiment 1 of the presentinvention will be described below.

FIG. 1, FIG. 2A and FIG. 2B shows a structure of the semiconductordevice according to Embodiment 1 of the present invention, wherein FIG.1 is a plan view, FIG. 2A is a section taken along the line IIa-IIa inFIG. 1, and FIG. 2B is a section taken along the line IIb-IIb in FIG. 1.

As shown in FIG. 1, FIG. 2A and FIG. 2B, an NMIS region 103 defined byan element isolation 102 and including a p-type well is formed in asemiconductor substrate 101 made of, for example, silicon. It should benoted that in the following description of the present embodiment, theNMIS region 103 means an active region of an N-type MIS transistorformed of the semiconductor substrate 101 and surrounded by the elementisolation 102. In the NMIS region 103, n-type source/drain diffusionlayers 118 are formed which serves as impurity diffusion layers to whichan n-type impurity ion such as arsenic is implanted. The n-typesource/drain diffusion layers 118 include n-type extension diffusionlayers 117 which are formed in regions below the sides of a gate portion113 (which will be described later) and of which junction depth iscomparatively shallow (see FIG. 2A).

Referring to the section taken along the line IIa-IIa in FIG. 1, on theNMIS region 103, a gate portion 113 is formed which composes the N-typeMIS transistor formed of, in the upward order, a gate insulating film111 and a gate electrode 112 (see FIG. 1 and FIG. 2A).

In contrast, referring to the section taken along the line IIb-IIb inFIG. 1, on the element isolation 102, the gate portion 113 is formedlikewise, and I-shaped (platy) offset spacers 114 made of an oxide filmare formed at the side faces of the gate portion 113. Further, L-shapedoxide films 115 in an L shape in section are formed at the side faces ofthe offset spacers 114 on the surface of the semiconductor substrate 101in the vicinity of the offset spacers 114, and sidewalls 116 made of SiNare formed so as to cover the side faces and the bottom faces of theL-shaped oxide films 115 (see FIG. 1 and FIG. 2B). The offset spacers114, the L-shaped oxide films 115, and the sidewalls 116 serve assidewall insulating films.

Further, as shown in FIG. 1, FIG. 2A and FIG. 2B, a liner film 135formed by LP-CVD and made of, for example, a nitride film having tensilestress is formed over the entirety of the semiconductor substrate 101 soas to cover the gate portion 113, the offset spacers 114, the L-shapedoxide films 115, and the sidewalls 116.

The method for manufacturing the semiconductor device according toEmbodiment 1 will be described below.

FIG. 3A to FIG. 3F, FIG. 4A to FIG. 4F, and FIG. 5A to FIG. 5F aresections of the semiconductor device in respective steps in a stepsequence of the semiconductor device manufacturing method according toEmbodiment 1 of the present invention, wherein FIG. 3A, FIG. 3C, FIG.3E, FIG. 4A, FIG. 4C, FIG. 4E, FIG. 5A, FIG. 5C, and FIG. 5E aresections in the step sequence corresponding to the section of FIG. 2A,and FIG. 3B, FIG. 3D, FIG. 3F, FIG. 4B, FIG. 4D, FIG. 4F, FIG. 5B, FIG.5D, and FIG. 5F are sections in the step sequence corresponding to thesection of FIG. 2B.

First, as shown in FIG. 3A and FIG. 3B, after the element isolation 102formed of SIT (shallow trench isolation) is formed in the semiconductorsubstrate 101 by an ordinary element isolation forming method, animpurity is implanted to the semiconductor substrate 101 to form theNMIS region 103 including the p-type well.

Next, as shown in FIG. 3C and FIG. 3D, an insulating film 131 is formedon the semiconductor substrate 101 by thermal oxidation or the like, anda polysilicon film 132 is formed on the insulating film 131.

Subsequently, as shown in FIG. 3E and FIG. 3F, patterning byphotolithography and dry etching is performed to form, on the NMISregion 103 and the element isolation 102, the gate portion 113 composingthe N-type MIS transistor formed of the gate insulating film 111 and thegate electrode 112 so that the gate portion 113 lies astride the NMISregion 103 (see FIG. 1).

Thereafter, as shown in FIG. 4A and FIG. 4B, an oxide film 133 is formedon the entirety of the semiconductor substrate 101 by, for example, CVD(chemical vapor deposition) so as to cover the side faces and the upperface of the gate portion 113.

Next, as shown in FIG. 4C and FIG. 4D, the oxide film 133 is etched backto form the I-shaped offset spacers 114 made of the oxide film at theside faces of the gate portion 113 on the NMIS region 103 and theelement isolation 102. Then, an n-type impurity such as arsenic isimplanted into the NMIS region 103 with the use of the gate portion 113and the I-shaped offset spacer 114 as a mask to form the n-typeextension diffusion layer 117 in a region below each side of the gateportion 113 of the N-type MIS transistor.

Subsequently, as shown in FIG. 4E and FIG. 4F, a silicon oxide film anda silicon nitride film are deposited in this order on the entirety ofthe semiconductor substrate 101.

Then, the silicon oxide film and the silicon nitride film are etchedsequentially by anisotropic dry etching to form the sidewalls 116 madeof the silicon nitride film at the side faces of the gate portion 113with the L-shaped oxide films 115 interposed.

Thereafter, as shown in FIG. 5A and FIG. 5B, an n-type impurity isimplanted into the NMIS region 103 with the use of the offset spacers114, the L-shaped oxide films 115, and the sidewalls 116 as animplantation mask. Then, thermal treatment is performed for activatingthe impurity to form the n-type source/drain diffusion regions 118.

Next, as shown in FIG. 5C and FIG. 5D, a resist pattern 134 open only ata part corresponding to the NMIS region 103 is formed on the elementisolation 102. Then, isotropic etching is performed using an aqueoussolution containing phosphoric acid with the use of the resist pattern134 as a mask to remove the sidewalls 116 in the NMIS region 103. Then,isotropic etching is performed using an aqueous solution containingfluoboric acid with the use of the resist pattern 134 as a mask toremove the offset spacers 114 and the L-shaped oxide films 115 in theNMIS region 103. Then, the resist pattern 134 is removed.

Subsequently, as shown in FIG. 5E and FIG. 5F, the liner film 135 madeof, for example, a nitride film is deposited on the entirety of thesemiconductor substrate 1 by LP-CVD so as to cover the gate portion 113,the offset spacers 114, the L-shaped oxide films 115, and the sidewalls116. A nitride film is employed as the liner film 135 herein. Wherein,the liner film 135 preferably has an internal stress of 1.5 GPa orlarger when it becomes at room temperature after deposition.

It is further preferable that the liner film 135 is deposited in anatmosphere of a gas having a high hydrogen rate by LP-CVD and thehydrogen composition rate in the film is reduced by performing thermaltreatment in the temperature range between 400° C. and 500° C. afterfilm formation. This increases the denseness of the liner film 135, sothat the liner film 135 contracts at room temperature to exert largetensile stress.

In the semiconductor device and the method for manufacturing itaccording to Embodiment 1 of the present invention, the sidewallinsulating films (the offset spacers 114, the L-shaped oxide films 115,and the sidewalls 116) of the gate portion 113 are removed in the NMISregion 103 including the p-type well and defined by the elementisolation 102 in the semiconductor substrate 101, while the sidewallinsulating films (the offset spacers 114, the L-shaped oxide films 115,and the sidewalls 116) of the gate portion 113 remain on the elementisolation 102 surrounding the NMIS region 103. Accordingly, the tensilestress that the liner film 135 has is applied to the channel region ofthe N-type MIS transistor efficiently, increasing the tensile stress inthe channel region of the N-type MIS transistor. This increases theelectron mobility in the channel region of the N-type MIS transistor toincrease the transistor power. The element isolation 102 is covered withthe resist pattern 134 when the sidewall insulating films in the NMISregion 103 are removed, thereby preventing etching damage to the elementisolation 102. When the element isolation 102 is damaged by etching, theNMIS region 103 is exposed to the air to form an interface state.However, the prevention of the etching damage suppresses formation ofthe interface state, preventing degradation of the transistorperformance.

It is noted that the offset spacers 114 are formed at the side faces ofthe gate portion 113 in the present embodiment but may not benecessarily formed. Further, the silicon nitride film is employed as thesidewalls 116 herein but another film is employable, such as a siliconoxide film, a PSG film, a BPSG film, a plasma oxide film, or a siliconoxynitride film. For example, when the sidewalls 116 are made of asilicon oxide film, the L-shaped oxide films 115 may not be formed.

In addition, all of the sidewall insulating films (the offset spacers114, the L-shaped oxide films 115, and the sidewalls 116) formed at theside faces of the gate portion 113 in the NMIS region 103 are removed inthe present embodiment, but only the sidewalls 116 may be removed of thesidewall insulating films formed at the side faces of the gate portion113 in the NMIS region 103 for the purpose of obtaining the same effectsas those in Embodiment 3, which will be described later.

Embodiment 2

A semiconductor device and a method for manufacturing it according toEmbodiment 2 of the present invention will be described below withreference to the drawings.

In the semiconductor device and the method for manufacturing itaccording to Embodiment 2 of the present invention, where an NMIS regionand a PMIS region are formed on the same semiconductor substrate, aconstitution and a method for obtaining it are provided in which theelectron mobility is increased in the channel region of the N-type MIStransistor while the hole mobility is decreased in the channel region ofthe P-type MIS transistor.

The semiconductor device according to Embodiment 2 of the presentinvention will be described below.

FIG. 6 shows a sectional structure of the semiconductor device accordingto Embodiment 2 of the present invention.

As shown in FIG. 6, an NMIS region 3 including a p-type well and a PMISregion 4 including an n-type well are formed in a semiconductorsubstrate made of, for example, silicon so as to be isolated from eachother by an element isolation 2. It should be noted that in thefollowing description of the present embodiment, the NMIS region 3 andthe PMIS region 4 mean an active region of an N-type MIS transistor andan active region of a P-type MIS transistor, respectively, which areformed in the semiconductor substrate 1 and are surrounded by theelement isolation 2. On the NMIS region 3, a gate portion 13 is formedwhich composes the N-type MIS transistor formed of, in the upward order,a gate insulating film 11 and a gate electrode 12. On the PMIS region 4,a gate portion 23 is formed which composes the N-type MIS transistorformed of, in the upward order, a gate insulating film 21 and a gateelectrode 22.

In the NMIS region 3, n-type source/drain diffusion regions 18 areformed which serve as impurity diffusion layers to which an n-typeimpurity ion such as arsenic is implanted. The n-type source/draindiffusion regions 18 have n-type extension diffusion layers 17 which areformed in regions below the side faces of the gate portion 13 and ofwhich junction depth is comparatively shallow. As well, in the PMISregion 4, p-type source/drain diffusion regions 28 are formed to which ap-type impurity such as boron is implanted and which have p-typeextension diffusion layers 27.

I-shaped (platy) offset spacers 24 made of an oxide film are formed atthe side faces of the gate portion 23 composing the P-type MIStransistor. L-shaped oxide films 25 are formed at the side faces of theoffset spacers 24 on the surface of the semiconductor substrate 1 in thevicinity of the offset spacers 24, and sidewalls 26 made of a siliconnitride film are formed so as to cover the side faces and the bottomfaces of the L-shaped oxide films 25.

Over the entirety of the semiconductor substrate 1, a liner film 35formed by LP-CVD and made of, for example, a nitride film having tensilestress is formed so as to cover the gate portion 13 in the NMIS region 3and the gate portion 23, the offset spacers 24, the L-shaped oxide films25, and the sidewalls 26 in the PMIS region 4.

The method for manufacturing the semiconductor device according toEmbodiment 2 will be described below.

FIG. 7A to FIG. 7D, FIG. 8A to FIG. 8D, and FIG. 9A to FIG. 9B aresections of the semiconductor device in respective steps in a stepsequence of the semiconductor device manufacturing method according toEmbodiment 2 of the present invention.

First, as shown in FIG. 7A, after the element isolation 2 formed of SITis formed in the semiconductor substrate 1 by an ordinary elementisolation forming method, an impurities are implanted to thesemiconductor substrate 1 to form the NMIS region 3 including the p-typewell and the PMIS region 4 including the n-type well in different steps.

Next, as shown in FIG. 7B, an insulating film 31 is formed on thesemiconductor substrate 1 by thermal oxidation or the like, and apolysilicon film 32 is formed on the insulating film 31.

Subsequently, as shown in FIG. 7C, patterning by photolithography anddry etching is performed to form the gate portion 13 composing theN-type MIS transistor formed of the gate insulating film 11 and the gateelectrode 12 on the NMIS region 3 and the gate portion 23 composing theP-type MIS transistor formed of the gate insulating film 21 and the gateelectrode 22 in the PMIS region 4.

Thereafter, as shown in FIG. 7D, an oxide film 33 is formed on theentirety of the semiconductor substrate 1 by for example, CVD so as tocover the side faces and the upper faces of the gate portion 13 and thegate portion 23.

Next, as shown in FIG. 8A, the oxide film 33 is etched back to form theoffset spacers 14 in an I-shape in section at the side faces of the gateportion 13 in the NMIS region 3 and the offset spacers 24 in an I shapein section at the side faces of the gate portion 23 in the PMIS region4. Then, an n-type impurity such as arsenic is implanted into the NMISregion 3 with the use of the gate electrode 12 and the offset spacers 14as a mask together with a resist mask (not shown) open at a partcorresponding to the NMIS region 3 to form the n-type extensiondiffusion layer 17 in a region below each side of the gate portion 13 ofthe N-type MIS transistor. As well, a p-type impurity such as boron isimplanted into the PMIS region 4 with the use of the gate electrode 22and the offset spacers 24 as a mask together with a resist mask (notshown) open at a part corresponding to the PMIS region 4 to form thep-type extension diffusion layer 27 in a region below each side of thegate portion 13 of the P-type MIS transistor.

Subsequently, as shown in FIG. 8B, a silicon oxide film and a siliconnitride film, for example, are deposited in this order on the entiretyof the semiconductor substrate 1.

Then, the silicon oxide film and the silicon nitride film are etchedsequentially by anisotropic dry etching to form the sidewalls 16 made ofthe silicon nitride film at the side faces of the gate portion 13 withthe L-shaped oxide films 15 interposed and to form the sidewalls 26 madeof the silicon nitride film at the side faces of the gate portion 26with the L-shaped oxide films 25 interposed.

Thereafter, as shown in FIG. 8C, an n-type impurity is implantedselectively into the NMIS region 3 with the use of the offset spacers14, the L-shaped oxide films 15, and the sidewalls 16 as an implantationmask. As well, a p-type impurity is implanted selectively into the PMISregion 4 with the use of the offset spacers 24, the L-shaped oxide films25, and the sidewalls 26 as an implantation mask. Then, thermaltreatment is performed for activating the impurities to form the n-typesource/drain diffusion regions 18 and the p-type source/drain diffusionregions 28.

Next, as shown in FIG. 8D, a resist pattern 34 open only at a partcorresponding to the NMIS region 3 is formed on the element isolation 2and the PMIS region 4. Herein, the resist pattern 34 is formed on theelement isolation 2 for preventing the element isolation 2 from beingdamaged by etching, which will be described later.

Thereafter, as shown in FIG. 9A, isotropic etching is performed using anaqueous solution containing phosphoric acid with the use of the resistpattern 34 as a mask to remove the sidewalls 16 in the NMIS region 3.Then, isotropic etching is performed using an aqueous solutioncontaining fluoboric acid with the use of the resist pattern 34 as amask to remove the L-shaped oxide film 15 and the offset spacers 14 inthe NMIS region 3. Then, the resist pattern 34 is removed. The elementisolation 2 is covered with the resist pattern 34 when the L-shapedoxide films 15 and the offset spacers 14 is removed, preventing theelement isolation 2 from being damaged.

Subsequently, as shown in FIG. 9B, the liner film 35 made of, forexample, a nitride film is deposited on the entirety of thesemiconductor substrate 1 by LP-CVD so as to cover the gate portion 13in the NMIS region 3 and the gate portion 23, the offset spacers 24, theL-shaped oxide films 25, and the sidewalls 26 in the PMIS region 4. Anitride film is employed as the liner film 35 herein. Wherein the linerfilm 35 preferably has an internal stress of 1.5 GPa or larger when itbecomes at room temperature after deposition.

It is further preferable that the liner film 35 is deposited in anatmosphere of a gas having a high hydrogen rate by LP-CVD and thehydrogen composition rate in the film is reduced by performing thermaltreatment in the temperature range between 400° C. and 500° C. afterfilm formation. This increases the denseness of the liner film 35, sothat the liner film 35 contracts at room temperature to exert largetensile stress.

In the semiconductor device and the method for manufacturing itaccording to Embodiment 2 of the present invention, where the NMISregion 3 and the PMIS region 4 are formed on the same semiconductorsubstrate 1, the sidewall insulating films (the offset spacers 14, theL-shaped oxide films 15, and the sidewalls 16) at the side faces of thegate portion 13 of the N-type MIS transistor are removed in the NMISregion 3. Accordingly, the tensile stress that the liner film 35 has isapplied efficiently to the channel region of the N-type MIS transistor,increasing the tensile stress in the channel region of the N-type MIStransistor. This increases the electron mobility in the channel regionof the N-type MIS transistor to increase the transistor power. On theother hand, in the PMIS region 4, which has no need to increase thedrivability, there remain the offset spacers 24, the L-shaped oxidefilms 25, and the sidewalls 26 at the side faces of the gate portion 23of the P-type MIS transistor, with no increase in tensile stress in thechannel region of the P-type MIS transistor.

Specifically, consider the case where the gate length of the transistorsis 50 nm and the tensile stress of the liner film is approximately 1.7GPa. In the channel region with the sidewall insulating films formed(the PMIS region 4 in the present embodiment), the tensile stress isapproximately 170 MPa and the electron mobility increases approximately2.5% while the hole mobility decreases approximately 5%. In the channelregion with no sidewall insulating films formed (the NMIS region 3 inthe present embodiment), the tensile stress is approximately 600 MPa(which is approximately four times that in the case with the sidewallinsulating films), and the electron mobility increases approximately 10%while the hole mobility decreases approximately 20%.

It is noted that the offset spacers 24 are formed at the side faces ofthe gate portion 23 in the present embodiment, but the offset spacers 24may not be necessarily formed. Also, the silicon nitride film isemployed as the sidewalls 26 herein but another film is employable suchas a silicon oxide film, a PSG film, a BPSG film, a plasma oxide film,or a silicon oxynitride film. For example, when the sidewalls are madeof a silicon oxide film, the L-shaped oxide films 25 may not be formed.

Embodiment 3

A semiconductor device and a method for manufacturing it according toEmbodiment 3 of the present invention will be described below withreference to the drawings.

In the semiconductor device and the method for manufacturing itaccording to Embodiment 3 of the present invention, where an NMIS regionand a PMIS region are formed on the same semiconductor substrate, aconstitution and a method for obtaining it are provided in which theelectron mobility is increased in the channel region of the N-type MIStransistor while the hole mobility is decreased in the channel region ofthe P-MIS transistor. Whereby, a semiconductor having high transistorpower (drivability) is realized.

The semiconductor device according to Embodiment 3 of the presentinvention will be described below.

FIG. 10 shows a sectional structure of the semiconductor deviceaccording to Embodiment 3 of the present invention.

The semiconductor device shown in FIG. 10 is different from thesemiconductor device according to Embodiment 2 in a point that sidewallinsulating films are provided at the side faces of the gate portion 13in the NMIS region 3, and the other aspects thereof are the same asthose in Embodiment 2. Specifically, the I-shaped spacers 14 made of anoxide film are formed at the side faces of the gate portion 13 of theNMIS region 3 and the L-shaped oxide films 15 are formed at the sidefaces of the offset spacers 14 on the surface of the semiconductorsubstrate 1 in the vicinity of the offset spacers 14, which is thedifference from the NMIS region 3 of the semiconductor device accordingto Embodiment 2.

Further, a liner film 42 formed by LP-CVD and made of, for example, anitride film having tensile stress is formed on the entirety of thesemiconductor substrate 1 so as to cover the gate portion 13, the offsetspacers 14, and the L-shaped oxide films 15 in the NMIS region 3 and thegate portion 23, the offset spacers 24, the L-shaped oxide films 25, andthe sidewalls 26 in the PMIS region 4.

The method for manufacturing the semiconductor device according toEmbodiment 3 will be described below.

FIG. 11A to FIG. 11C are sections of the semiconductor device inrespective steps in a step sequence of the semiconductor devicemanufacturing method according to Embodiment 3 of the present invention.Of the steps in the semiconductor device manufacturing method accordingto Embodiment 3 of the present invention, description of the commonsteps to those of the semiconductor device manufacturing methodaccording to Embodiment 2 are omitted, and the different features aredescribed mainly.

First, the aforementioned steps shown in FIG. 7A to FIG. 7D and FIG. 8Ato FIG. 8C are performed likewise.

Next, as shown in FIG. 11A, a resist pattern 41 is formed on the PMISregion 4 except on the element isolation 2. Herein, the resist pattern41 is not formed on the element isolation 2, which is different from theresist pattern 34 in Embodiment 3, because the element isolation 2 isfree from damage by etching, which will be described later. However, itis needless to say that the resist pattern 41 may be formed also on theelement isolation 2 similarly to the aforementioned resist pattern 34.

Subsequently, as shown in FIG. 11B, isotropic etching is performed usingan aqueous solution containing phosphoric acid with the use of theresist pattern 41 as a mask to remove the sidewalls 16 in the NMISregion 3. Then, the resist pattern 41 is removed. It is noted thatremoval of the sidewall 16 with the use of the aqueous solutioncontaining phosphoric acid causes no damage to the element isolation 2.

Thereafter, as shown in FIG. 11C, the liner film 42 made of, forexample, a nitride film having tensile stress is deposited on theentirety of the semiconductor substrate 1 by LP-CVD so as to cover thegate portion 13, the offset spacers 14, and the L-shaped oxide films 15in the NMIS region 3 and the gate portion 23, the offset spacers 24, theL-shaped oxide films 25, and the sidewalls 26 in the PMIS region 4.Similarly to that in Embodiment 1, the liner film 42 preferably has aninternal stress of 1.5 GPa or larger when it becomes at room temperatureafter deposition. It is also preferable that the liner film 42 isdeposited in an atmosphere of a gas having a high hydrogen rate byLP-CVD and the hydrogen composition rate in the film is reduced byperforming thermal treatment in the temperature range between 400° C.and 500° C. after film formation.

In the semiconductor device and the method for manufacturing itaccording to Embodiment 3 of the present invention, where the NMISregion 3 and the PMIS region 4 are formed in the same semiconductorsubstrate, only the offset spacers 14 and the L-shaped oxide films 15are formed at the side faces of the gate portion 13 in the N-type MIStransistor with the sidewalls 16 removed. Partial removal of thesidewall insulating films at the side faces of the gate portion 13 inthe N-type MIS transistor leads to efficient application of the tensilestress that the liner film 42 has to the channel region of the N-typeMIS transistor, though it is less applied than in Embodiment 2, theground of which will be described later. Accordingly, the tensile stressis increased in the channel region of the N-type MIS transistor toincrease the electron mobility in the channel region of the N-type MIStransistor, resulting in an increase in transistor power. Also, theoffset spacers 14 and the L-shaped oxide films 15 remain at the sidefaces of the gate portion 13 of the N-type MIS transistor, which is thedifference from that in Embodiment 2. Accordingly, damage by etching tothe surface of the semiconductor substrate 1 is reduced, and a regionwhere the liner film 42 is in direct contact with the semiconductorsubstrate 1 is reduced, thereby suppressing formation of an interfacestate which would involve an adverse influence on the characteristic ofthe transistors. On the other hand, in the PMIS region 4, which has noneed to increase the drivability, the offset spacers 24, the L-shapedoxide films 25, and the sidewalls 36 remain at the side faces of thegate portion 23 of the P-type MIS transistor, resulting in no increasein tensile stress in the channel region of the P-type MIS transistor.

Specifically, consider the case where the gate length of the transistorsis 50 nm and the internal stress of the liner film is approximately 1.7GPa. In the channel region with the sidewall insulating films formed(the PMIS region 4 in the present embodiment), the tensile stress isapproximately 170 MPa and the electron mobility increases approximately2.5% while the hole mobility decreases approximately 5%. In the channelregion with a part of the sidewall insulating films removed (the NMISregion 3 where the sidewalls 16 are removed in the present embodiment),the tensile stress is approximately 250 MPa and the electron mobilityincreases approximately 4% while the hole mobility decreasesapproximately 7.5%.

It is noted that the gate portion 13 formed on the NMIS region 3 inEmbodiments 2 and 3 may be formed on also the element isolation 2 so asto lie astride the NMIS region 3 as in Embodiment 1. In this case, thesidewall insulating films at the NMIS region 3 may be removed withoutremoving the sidewall insulating films on the element isolation 2 as inEmbodiments 2 and 3.

In addition, the carrier mobility changes depending on the type of thecarriers and a direction of carrier conduction, and therefore, may bedesigned appropriately according to the channel direction to be set.

The present invention is useful for a method for manufacturing asemiconductor device having high transistor power.

1. A semiconductor device, comprising: a semiconductor substrate; anelement isolation; a first MIS transistor on the semiconductorsubstrate; and an insulating film which has tensile stress and which isformed on the semiconductor substrate so as to cover the first MIStransistor, wherein the first MIS transistor includes: a p-typesemiconductor layer defined by the element isolation in thesemiconductor substrate; a first gate insulating film formed on thep-type semiconductor layer; a first gate electrode formed on the firstgate insulating film, the first gate electrode having a first portiondisposed on the p-type semiconductor layer and a second portion disposedon the element isolation so as to lie astride the p-type semiconductorlayer; a first sidewall insulating film formed at each side face of thesecond portion of the first gate electrode on the element isolation andincluding at least a first sidewall; an n-type extension diffusion layerformed outwards from the first portion of the first gate electrode inthe p-type semiconductor layer; and an n-type impurity diffusion layerformed in a region of the p-type semiconductor layer which is adjacentto the n-type extension diffusion layer, wherein the first sidewallinsulating film is not formed at each side face of the first portion ofthe first gate electrode on the p-type semiconductor layer.
 2. Thesemiconductor device of claim 1, further comprising a second MIStransistor, wherein the second MIS transistor includes: an n-typesemiconductor layer defined by the element isolation in thesemiconductor substrate; a second gate insulating film formed on then-type semiconductor layer; a second gate electrode formed on the secondgate insulating film; a second sidewall insulating film formed at eachside face of the second gate electrode and including at least a secondsidewall; a p-type extension diffusion layer formed outwards from thesecond gate electrode in the n-type semiconductor layer; and a p-typeimpurity diffusion layer formed in a region of the n-type semiconductorlayer which is adjacent to the p-type extension diffusion layer, and theinsulating film having tensile stress further covers the second MIStransistor.
 3. The semiconductor device of claim 1, wherein the firstsidewall insulating film further includes an L-shaped insulating film inan L shape in section disposed between the first sidewall and the eachside face of the second portion of the first gate electrode and betweenthe first sidewall and the element isolation, and a third sidewallinsulating film made of the L-shaped insulating film disposed on theeach side face of the first portion of the first gate electrode on thep-type semiconductor layer.
 4. The semiconductor device of claim 1,wherein the insulating film having tensile stress is formed so as to bein contact with a side surface of the first portion of the first gateelectrode.
 5. The semiconductor device of claim 1, wherein the firstsidewall is made of a silicon nitride film.
 6. The semiconductor deviceof claim 1, wherein the insulating film having tensile stress is made ofa silicon nitride film.
 7. The semiconductor device of claim 1, whereinthe channel direction in the first MIS transistor is set along a crystalorientation of <110> in the semiconductor substrate.
 8. Thesemiconductor device of claim 3, wherein the L-shaped insulating filmincludes: a first insulating film in an I shape in section disposed onthe each side face of the first gate electrode; and a second insulatingfilm in an L shape in section disposed on a side face of the firstinsulating film.
 9. The semiconductor device of claim 3, wherein theinsulating film having tensile stress is formed so as to be in contactwith a L-shaped surface of the third sidewall insulating film.
 10. Thesemiconductor device of claim 3, wherein the first sidewall is made of asilicon nitride film, and the L-shaped insulating film is made of anoxide film.
 11. A semiconductor device, comprising: a semiconductorsubstrate; an element isolation; a first MIS transistor and a second MIStransistor, the first MIS transistor and the second MIS transistor beingformed in the semiconductor substrate; and an insulating film havingtensile stress which is formed on the semiconductor substrate so as tocover the first MIS transistor and the second MIS transistor, whereinthe first MIS transistor includes: a p-type semiconductor layer definedby the element isolation in the semiconductor substrate; a first gateinsulating film formed on the p-type semiconductor layer; a first gateelectrode formed on the first gate insulating film; an n-type extensiondiffusion layer formed outwards from the first gate electrode in thep-type semiconductor layer; and an n-type impurity diffusion layerformed in a region of the p-type semiconductor layer which is adjacentto the n-type extension diffusion layer, the second MIS transistorincludes: an n-type semiconductor layer defined by the element isolationin the semiconductor substrate; a gate insulating film formed on then-type semiconductor layer; a second gate electrode formed on the secondgate insulating film; a first sidewall insulating film formed at eachside face of the second gate electrode and including at least a firstsidewall; a p-type extension diffusion layer formed outwards from thesecond gate electrode in the n-type semiconductor layer; and a p-typeimpurity diffusion layer formed in a region of the n-type semiconductorlayer which is adjacent to the n-type extension diffusion layer, and thefirst sidewall insulating film includes an L-shaped insulating film inan L shape in section disposed between the first sidewall and each sideface of the second gate electrode and between the first sidewall and then-type semiconductor layer, and the first sidewall is not formed at eachside of the first gate electrode and a second sidewall insulating filmmade of the L-shaped insulating film is formed at each side face of thefirst gate electrode.
 12. The semiconductor device of claim 11, whereinthe L-shaped insulating films included in the first sidewall insulatingfilm includes an I-shaped insulating film in an I shape in section whichis formed at each side face of the first gate electrode and the secondgate electrode and a second insulating film in an L shape in sectionwhich is formed at the side face of the I-shaped insulating film. 13.The semiconductor device of claim 11, wherein the insulating film havingtensile stress is formed so as to be in contact with a L-shaped surfaceof the second sidewall insulating film.
 14. The semiconductor device ofclaim 11, wherein the first sidewall is made of a silicon nitride film.15. The semiconductor device of claim 11, wherein the insulating filmhaving tensile stress is made of a silicon nitride film.